There are a number of sport surfaces, or floor systems, that have been developed to provide safety and protection for athletes, dancers, and the like engaged in active sport applications. These sport surfaces function to absorb shock, reduce fatigue, limit injury, and enhance performance. Some sport surfaces are supported by foam backing or rubber feet, others are cushioned mechanically through the inclusion of springs, and still others use a combination of springs and foam cubes.
In gymnastics, the “floor” or “spring floor” refers to a specially prepared sport surface, which is considered an apparatus. It is used by both male and female gymnasts. The event in gymnastics performed on such a spring floor is known as floor exercise. A typical spring floor contains springs and/or foam rubber cubes. A plywood floor overlies the springs and/or foam rubber cubes. The plywood floor may then be covered with additional foam and a top layer of carpet. The intent of this spring floor structure is to make the floor bouncy, soften the impact of landings, and enable the gymnast to gain height when tumbling.
On other gymnastics apparatuses athletes can rely on their own strength to lift, support, or swing their bodies. However, in floor exercise, a great deal of the athlete's performance is due, not only to their own strength and control, but additionally to the rebounding effect of the spring floor. Gymnasts can range in age from eight or nine to almost thirty years of age. An eight year old gymnast may weigh as little as sixty pounds, whereas, a fully mature athlete may weigh one hundred forty pounds or more.
Unfortunately, existing spring floor systems fail to provide adjustability for the differing sizes, and more specifically, the differing weights of gymnasts. That is, lighter weight gymnasts jump and land on the same spring floor system as heavier weight gymnasts. The heavier weight gymnasts will get more “spring” or rebound from the spring floor because they are able to more effectively compress the floor materials, particularly the springs or cubes in the spring floor. Thus, the spring floor feels bouncy to a heavier gymnast. In contrast, the spring floor will feel relatively hard to a lighter weight gymnast whose weight will only just barely compress the springs or cubes.
This discrepancy can result in competitive disadvantages, even within the same age groups or competition levels since athletes come in different weights. Prior art spring floors suffer from other problems as well. For example, some prior art spring floors make a cupping motion under the athlete when the athlete lands. The pressure caused by this cupping results in the most force on the medial aspect of the foot. The intensity of this force on the feet, legs, and knees combined with the repetitions involved in training and competition can cause many types of injuries. Furthermore, since the spring floor barely compresses for a lighter weight gymnast, he or she may be at even greater risk of injury.
A floor exercise routine can include three, four, or five major tumbling passes and several major dance skills, turns and leaps. In each tumbling sequence, the gymnast links several acrobatic skills in a series, which generally culminates with an acrobatic flight skill. To achieve the acrobatic skills, the gymnast must change the horizontal velocity created by the preceding linked tumbling skills into vertical velocity. This explosive movement immediately precedes the somersault and is called a “take-off.”
During a tumbling take-off, a gymnast may impact the floor surface from either a forward- or backward-facing body orientation, and may rebound into an aerial somersault that rotates either forward or backward. It has been observed through recordation using high speed video, that gymnasts typically bend their knees twice during the execution of a backward tumbling take-off, referred to herein as a “double knee bend.” The first knee bend is initiated by the gymnast when executing the backward tumbling take-off. However, it is believed that the second knee bend is not intended by the gymnast. Rather, it is hypothesized that the second knee bend may be due to the recoil of the spring floor and the nature of the floor's fundamental frequency. The fundamental frequency of the spring floor is approximately twice that of the gymnast. Therefore, the floor does not move in synchrony with the gymnast's take off actions. Rather, the “rhythm” of the floor's movements are about twice as fast as the gymnast's down-and-up movements during a tumbling takeoff.
When performing a backward tumbling take-off the gymnast typically experiences dorsiflexion, a movement which decreases the angle between the foot and the leg. That is, the toes move toward the shin. If this dorsiflexion is combined with an upward thrust, i.e., recoil movement, of the floor and/or an extension of the knee, a ruptured Achilles tendon and/or anterior talotibial impingement (bumping the talus into the mortice formed by the tibia and fibula) may occur. A rupture of the Achilles tendon can be a debilitating injury that may require surgical repair, and thus limit or end the career of an elite gymnast.